U.S. patent number 7,125,441 [Application Number 11/060,690] was granted by the patent office on 2006-10-24 for corrosion inhibiting materials for reducing corrosion in metallic concrete reinforcements.
This patent grant is currently assigned to Cortec Corporation. Invention is credited to Arthur H. Ahlbrecht, Alla Furman, Margarita Kharshan, Boris A. Miksic.
United States Patent |
7,125,441 |
Furman , et al. |
October 24, 2006 |
Corrosion inhibiting materials for reducing corrosion in metallic
concrete reinforcements
Abstract
A corrosion inhibiting composition for use in reinforced
concrete structures, the inhibitor composition reducing the rate of
corrosion in metallic reinforcing rods placed within the
structures. The composition includes a combination of one or more
corrosion inhibiting agents and one or more silica neutralizing
agents.
Inventors: |
Furman; Alla (Shoreview,
MN), Kharshan; Margarita (Little Canada, MN), Miksic;
Boris A. (North Oaks, MN), Ahlbrecht; Arthur H.
(Stillwater, MN) |
Assignee: |
Cortec Corporation (St. Paul,
MN)
|
Family
ID: |
37110505 |
Appl.
No.: |
11/060,690 |
Filed: |
February 17, 2005 |
Current U.S.
Class: |
106/14.42;
106/14.41; 106/640; 106/642; 106/644; 106/643; 106/641; 106/14.44;
106/14.13 |
Current CPC
Class: |
C04B
28/02 (20130101); C04B 40/0039 (20130101); C23F
11/10 (20130101); C23F 11/12 (20130101); C23F
11/141 (20130101); C23F 11/181 (20130101); C04B
40/0039 (20130101); C04B 22/085 (20130101); C04B
24/06 (20130101); C04B 24/12 (20130101); C04B
40/0039 (20130101); C04B 22/085 (20130101); C04B
24/04 (20130101); C04B 24/06 (20130101); C04B
28/02 (20130101); C04B 22/085 (20130101); C04B
24/06 (20130101); C04B 24/122 (20130101); C04B
32/02 (20130101); C23F 11/08 (20130101) |
Current International
Class: |
C23F
11/00 (20060101); C04B 103/61 (20060101); C04B
24/06 (20060101); C23F 15/00 (20060101) |
Field of
Search: |
;106/14.13,14.41,14.42,14.44,640,641,642,643,644 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
0614860 |
|
Sep 1994 |
|
EP |
|
54-32145 |
|
Mar 1979 |
|
JP |
|
WO 2004/044267 |
|
May 2004 |
|
WO |
|
Primary Examiner: Green; Anthony J.
Attorney, Agent or Firm: Haugen Law Firm PLLP
Claims
What is claimed is:
1. A corrosion inhibiting composition, comprising; (a) between
about 8.5% and about 17.5% by weight of one or more gluconate
salts; (b) between about 18% and about 26% by weight of one or more
nitrate salts; and (c) between about 2.5% and about 19.5% by weight
of one or more corrosion inhibiting agents selected from the group
consisting of cyclohexylammonium benzoate, ethylammonium benzoate,
ammonium benzoate, dimethylethanolamine, and combinations
thereof.
2. A corrosion inhibiting composition as in claim 1 wherein said
one or more gluconate salts are selected from the group consisting
of zinc gluconate, potassium gluconate, ammonium gluconate, and
combinations thereof.
3. A corrosion inhibiting composition as in claim 1 wherein said
one or more nitrate salts are selected from the group consisting of
lithium nitrate, calcium nitrate, aluminum nitrate, and
combinations thereof.
4. A method for inhibiting corrosion of metallic elements disposed
in concrete mixtures, said method comprising the steps of; (a)
providing a corrosion inhibiting composition having: (i) between
about 8.5% and about 17.5% by weight of one or more gluconate
salts; (ii) between about 18% and about 26% by weight of one or
more nitrate salts; and (iii) between about 2.5% and about 19.5% by
weight of one or more corrosion inhibiting agents; (iv) balance
water; and (b) adding said corrosion inhibiting composition to said
concrete mixtures.
5. A method as in claim 4 wherein said concrete mixtures are
pre-cured, wet concrete.
6. A method as in claim 4 wherein said concrete mixtures are in the
form of cured concrete structures having one or more of said
metallic elements embedded therein.
7. A method as in claim 4 wherein said corrosion inhibiting
composition is added to said concrete mixtures at a concentration
of between 16 and 96 ounces per cubic yard of concrete mixture.
8. A corrosion inhibiting composition for treatment of metallic
elements disposed within concrete mixtures, said corrosion
inhibiting composition comprising: (a) between about 8.5% and about
17.5% by weight sodium gluconate; (b) between about 18% and about
26% by weight aluminum nitrate; and (c) between about 2.5% and
about 19.5% by weight of one or more corrosion inhibiting agents
other than gluconate salts and nitrate salts.
9. A corrosion inhibiting composition consisting essentially of:
(a) about 9.5% by weight sodium gluconate; (b) about 18% by weight
aluminum nitrate; (c) about 19.5% by weight of one or more
corrosion inhibiting agents; and (d) balance water.
10. A corrosion inhibiting composition as in claim 9 wherein said
one or more corrosion inhibiting agents are selected from the group
consisting of methylethanolamine, cyclohexylamine, and benzoic
acid.
Description
FIELD OF THE INVENTION
The present invention relates generally to corrosion inhibiting
materials for use in reinforced concrete structures, and more
particularly to materials incorporating one or more corrosion
inhibiting agents and one or more silica neutralizing agents for
reducing the rate of corrosion in metallic reinforcing rods placed
within structures formed of concrete. The materials of the present
invention are designed for use either in admixture with raw
concrete when provided on an in-situ basis within the concrete
mixing, or alternatively may be effectively utilized as surface
treatments on existing concrete structures having
corrosion-susceptible elements disposed therewithin. Preferably,
the materials of present invention do not adversely affect the
performance characteristics of the concrete.
BACKGROUND OF THE INVENTION
Concrete structures, particularly highways and bridges, typically
utilize metallic reinforcement members embedded therewithin to
provide stability and additional strength to the concrete, as well
as to enhance the ability of the concrete to withstand shear
forces. These reinforcements are used in a variety of
configurations, and are typically present in the form of
reinforcing rods, wire mesh, metallic fibers, and the like.
Reinforcements are usually situated within the cured concrete by
pouring raw or uncured concrete therearound or, in the case of
metallic fibers, added during the concrete mixing operation for
subsequent curing. The term "raw concrete" is utilized herein in a
comprehensive sense, and is intended to relate to wet workable
concrete mixtures which have not yet cured to their solid form.
Upon the passage of time, the metallic reinforcements have a
tendency to corrode as external elements including moisture and
pollutants such as carbon dioxide, oxides of sulfur, oxides of
nitrogen, hydrogen sulfide, and road treatment chemicals permeate
along and through the concrete structure and reach the surface of
the metal reinforcement. When utilized, for example, in highways,
bridges, and parking structures, chlorides including sodium
chloride and calcium chloride may permeate the concrete structure
due to the widespread utilization of such materials as a mechanism
to melt ice and snow from the road surfaces. Both calcium chloride
and sodium chloride are widely used for this purpose, and their
use, although necessary for safety reasons, has been linked to the
rapid deterioration of certain concrete structures.
A characteristic of common concrete mixtures that exacerbates
corrosion of, for example, metallic elements embedded within a mass
of concrete is alkaline silica reactivity (ASR), a condition in
which alkali in cement attacks silica-based aggregates to form gels
that can absorb water. Such water absorption can lead to crack
formation in the concrete mass due to freeze-thaw cycles, as well
as the reception and retention of moisture adjacent to metallic
elements that may corrode in the presents of water. One approach to
reduce and/or eliminate the alkaline silica reactivity in concrete
admixtures is through the use of lithium salts such as lithium
nitrate to neutralize the silica found in common concrete admixture
recipes. An example of the use of lithium salts to thwart alkaline
silica reactivity in concrete mixtures is found in WO 04044267
published in the name of the Virginia Transportation Research
Counsel. Though the use of lithium salts has proven to be
beneficial in minimizing alkaline silica reactivity in concrete
mixtures, such utility alone does not provide a total preventative
and/or restorative corrosion protection solution for
corrosion-susceptible elements disposed in concrete mixtures.
In order to facilitate the access of corrosion inhibiting materials
to concrete reinforcements, it is normally desirable for such
materials to be added to the raw concrete mixture in order to
provide for contact with the surfaces of the metallic reinforcement
members or structures prior to concrete curing. The corrosion
inhibiting materials added in this fashion normally migrate
throughout the concrete mixture at a rate sufficient to provide
ongoing protection over relatively extended periods of time, and
hence have the ability to protect the metallic reinforcements over
such extended periods of time.
In other embodiments however, such corrosion inhibiting materials
need to be applied to cured concrete structures having
corrosion-susceptible reinforcements encased therewithin. As such,
the corrosion inhibiting materials are preferably applied to the
surface of the concrete structure and thereafter migrate inwardly
to protect the surface of the metallic reinforcements.
As a further aspect of corrosion inhibiting materials, it is a
common objective to utilize ecologically friendly components
wherever possible. In this connection, the formulation of the
present invention preferably provides for the use of ecologically
friendly materials, and thus the goals and objectives of inhibiting
corrosion in large structures can be undertaken without
significantly contributing to the release of ecologically harmful
products into the environment.
In view of the above, it is therefore a principal object of the
present invention to provide a corrosion inhibiting composition
that may be applied to raw or cured concrete mixtures for
protecting corrosion-susceptible elements disposed within such
concrete mixtures, with the corrosion inhibiting composition
incorporating one or more alkaline silica reactivity suppression
agents and one or more corrosion inhibiting agents.
It is a further object of the present invention to provide a
corrosion inhibiting composition having the capability to migrate
within cured concrete mixtures along the surface of embedded
corrosion-susceptible elements so as to provide corrosion
protection thereto over a prolonged period of time.
It is a further object of the present invention to provide a
corrosion inhibiting composition comprising ecologically friendly
components.
It is a still further object of the present invention to provide a
corrosion inhibiting composition for protection of metallic
reinforcements embedded within concrete mixtures without adversely
affecting the curing rate or ultimate strength of the respective
concrete mixtures.
Other objects of the present invention will become apparent to
those skilled in the art upon a study of the following
specification and appended claims.
SUMMARY OF THE INVENTION
In accordance with the present invention, a formulation has been
developed which is readily adapted for use in admixture with raw or
wet concrete mixtures, as well as in surface treatment of formed
concrete structures, and which provides long-lasting and reliable
corrosion inhibiting properties for metallic reinforcements. When
employed in admixture with raw concrete, the formulations of the
present invention provide the dual function of corrosion inhibition
and controlling expansion from the alkali silica reaction.
In a particular embodiment, the corrosion inhibiting composition of
the present invention includes a combination of one or more
corrosion inhibiting agents and one or more silica neutralizing
agents. Preferably, the silica neutralizing agents include between
about 5% and about 30% by weight of one or more gluconate salts,
and between 2.5% and 40% by weight of one or more nitrate salts.
The corrosion inhibiting agents are preferably presents in the
composition of the present invention at a concentration of between
about 1% and about 20% by weight.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The objects and advantages enumerated above together with other
objects, features, and advances represented by the present
invention will now be presented in terms of detailed embodiments.
Other embodiments and aspects of the invention are recognized as
being within the grasp of those having ordinary skill in the
art.
The present invention is specifically directed to corrosion
inhibiting compositions that employ one or more corrosion
inhibiting agents and one or more silica neutralizing agents to
suppress alkaline silica reactivity in concrete mixtures.
Particular silica neutralizing agents useful in the compositions of
the present invention include gluconate salts and/or nitrate salts.
Examples of gluconate salts known to be useful in the compositions
of the present invention include sodium gluconate, zinc gluconate,
potassium gluconate, and ammonium gluconate. Examples of nitrate
salts useful in the compositions of the present invention include
lithium nitrate, calcium nitrate, and aluminum nitrate. The above
examples, however, are not intended to be comprehensive of those
materials useful as silica neutralizing agents in the present
invention, but rather to provide specific components readily known
to be useful as silica neutralizing agents.
In some embodiments for the present invention, mixtures of
gluconate salts and nitate salts are used as the silica
neutralizing agents in an amount ranging from 5% to 30% by weight
gluconate salts, and 2.5% to 40% nitrate salts. Generally, and for
most purposes, a ratio of between about 5% by weight and 30% by
weight gluconate salts is preferred, with a specific formulation of
25% by weight gluconate salts having been found to be highly
effective.
To complete the corrosion inhibiting composition solutions of the
present invention, known corrosion inhibitors such as, for example,
amino alcohols, amino silane, amine salts, and amino carboxylates
such as ammonium benzoate are added. Such corrosion inhibiting
materials are disclosed in, for example, U.S. Pat. Nos. 5,597,514
and 5,750,053, which are assigned to the same assignee as in the
present application, and are incorporated herein by reference.
Preferably, such corrosion inhibitors are added to the solution at
a concentration of between about 1% and 20% by weight, with a range
of between 2.5 and 10% by weight of the solution being most
preferred. The solutions of the present invention therefore
preferably include between 5 and 30% by weight gluconate salts,
between 2.5% and 40% by weight nitrate salts, and between 1% and
20% by weight corrosion inhibiting agents, balance water
When added to raw or wet concrete, an amount of between about 16
ounces and 96 ounces of solution per cubic yard of raw concrete has
been found highly effective, although amounts as low as 5 ounces of
inhibiting solution per cubic yard of raw concrete have also been
found to be useful.
The following examples provide various particular embodiments of
the inhibiting composition solutions of the present invention. It
is contemplated that such compositions represent exemplary
formulations only, and that many other formulations incorporating
the components of the present invention may be derived with
successful results, and are within the scope of the present
invention:
EXAMPLE I
A corrosion inhibiting solution was prepared in accordance with the
following formulation:
TABLE-US-00001 Component Percent by Weight Sodium Glucoheptonate
8.5% by weight Cyclohexylammonium benzoate 1.25% by weight
Ethylammonium benzoate 1.25% by weight Calcium nitrate 55% by
weight Water 34% by weight
This formulation is provided in admixture with raw concrete in an
amount of 64 ounces by weight per cubic yard of concrete for
inhibiting the corrosion of metallic reinforcements.
EXAMPLE II
A corrosion inhibiting solution was prepared in accordance with the
following formulation:
TABLE-US-00002 Component Percent by Weight Sodium glucoheptonate
8.5% by weight Ethylammonium benzoate 1.25% by weight
Cyclohexylammonium benzoate 1.25% by weight Lithium nitrate 24% by
weight Water 65% by weight
This formulation is provided in admixture with raw concrete in an
amount of 64 ounces by weight per cubic yard of raw concrete for
inhibiting the corrosion of metallic reinforcements.
EXAMPLE III
A corrosion inhibiting solution was prepared in accordance with the
following formulation:
TABLE-US-00003 Component Percent by Weight Sodium gluconate 17.5%
by weight Ammonium Benzoate 2.5% by weight Lithium Nitrate 26% by
weight Water 54% by weight
This formulation was provided in admixture with raw concrete in an
amount of 64 ounces by weight per cubic yard of raw concrete for
inhibiting the corrosion of metallic reinforcements.
EXAMPLE IV
A corrosion inhibiting solution prepared in accordance with the
following formulation was used as a control to determine the
corrosion improvement resulting from the nitrate salts
addition:
TABLE-US-00004 Component Percent by Weight Sodium Glucoheptonate
25% by weight Ammonium benzoate 10% by weight Water 65% by
weight
This formulation was provided in admixture with raw concrete in an
amount of 32 ounces by weight per cubic yard of raw concrete for
inhibiting the corrosion of metallic reinforcements. It is possible
that if the dosage rate of this product was doubled the corrosion
protection would be higher but the set time of the concrete would
be excessive (see Table 1) and the amount of sodium introduced in
the concrete would be excessive.
EXAMPLE V
A corrosion inhibiting solution was prepared in accordance with the
following formulation:
TABLE-US-00005 Component Percent by Weight Sodium Gluconate 8.5% by
weight Cyclohexylammonium benzoate 1.25% by weight Ethylammonium
benzoate 1.25% by weight Calcium nitrate 13% by weight Lithium
nitrate 9% by weight Water 67% by weight.
This formulation is provided in admixture with raw concrete in an
amount of 64 ounces by weight per cubic yard.
EXAMPLE VI
A corrosion inhibiting solution was prepared in accordance with the
following formulation:
TABLE-US-00006 Component Percent by Weight Sodium Gluconate 9.5% by
weight Methylethanolamine 2.0% by weight Aluminum nitrate 18% by
weight Cyclohexyl amine 14% by weight Benzoic acid 3.5% by weight
Water 53% by weight
This formulation is provided in admixture with raw concrete in an
amount of 64 ounces by weight per cubic yard.
EXAMPLE VII
A corrosion inhibiting solution was prepared in accordance with the
following formulation:
TABLE-US-00007 Component Percent by Weight Lithium nitrate 25% by
weight Dimethylethanolamine 2.5% by weight Water 72.5% by
weight
This formulation is provided in admixture with raw concrete in an
amount of 64 ounces by weight per cubic yard.
TABLE-US-00008 TABLE 1 To evaluate set time samples were checked
every 15 minutes. Material Set Time Example 1 3 hr 50 min Example 2
3 hr 50 min Example 3 3 hr 50 min Example 4 5 hr 15 min Example 5 3
hr 50 min Example 6 3 hr 50 min Example 7 2 hr 30 min
Before impedance measurements were taken the molded concrete
samples were cured at room temperature in a relative humidity of 95
98% for 28 days. After curing the samples were immersed in 3% NaCL
solution for 20 hours.
TABLE-US-00009 TABLE 2 The samples were evaluated with Impedance
testing (ASTM G106-89) as follows: The working electrode was a
cleaned carbon steel standard rebar embedded in mortar which was
prepared with the inhibitor solution at the amount equivalent to
either 32 ounces or 64 ounces per cubic yard of concrete. Corrosion
Polarization Current, Corrosion Z, Resistance Icorr. Rate,
Protection Material Rp, ohm .mu.A/cm.sup.2 .mu.m/year power, %
Control 2924 .59 6.8 -- Example 1 11403 .15 1.7 75 Example 2 24915
.07 .8 88.3 Example 3 11473 .15 1.7 75 Example 4 6449 .27 3.1 55
Example 5 18550 .09 1.0 85 Example 6 53300 .003 0.3 96 Example 7
20602 .10 1.15 83.1
The concentration of inhibitor corresponds to 4 lb per cubic yard
for all of the samples except Number 4 which was 2 lb per cubic
yard due to sodium and set time limitations. Calculations were
carried out using formulas: Icorr=26 mV/(Rp*Surface area); 1
.mu.A/cm.sup.2=11.6 .mu.m/year Surface area=15 cm.sup.2
Z=100%*(Icorr.Cont.-Icorr.)/Icorr.Cont
These results clearly indicate that gluconate salts such as sodium
gluconate in combination with nitrate salts such as
Ca(NO.sub.3).sub.2 and LiNO.sub.3, when used in compositions
including corrosion inhibiting agents substantially decrease the
corrosion rate of embedded metallic elements.
* * * * *